1. Technical Field
This invention concerns a bumper bar for vehicles.
2. Description of the Background Art
A completed vehicle is subject to many requirements and wishes. One of these is that the vehicle is to protect passengers and load during a collision. This is achieved in that different parts in and on the vehicle are designed and constructed such that they in different ways absorb, distribute and channel energy during a collision.
If the transfer of energy from a collision object to the vehicle is limited, for example, if the vehicle collides with a collision object at low speed, the parts must principally absorb and distribute the forces such that as little change of shape of the vehicle and its parts occurs as possible. It is most preferable if the change of shape is only temporary, something that is known as xe2x80x9celastic deformationxe2x80x9d.
If the transfer of energy from the collision object to the vehicle is large, as occurs, for example, if the vehicle collides with a collision object at high speed, the energy-absorbing parts must absorb and distribute the forces in such a way that the energy is used in a controlled manner as far as this is possible; by using the energy, for example, for the demolition of certain predetermined parts of the vehicle that have been constructed for this purpose and that can be easily replaced after the collision. This is normally called xe2x80x9cplastic deformationxe2x80x9d.
The vehicle must also have a shape that gives the desired driving properties, external and internal dimensions and spaces. The vehicle must also have an appearance that corresponds to the wishes and expectations of the customers. There are often conflicts between the traffic safety of a vehicle and its design. Small, fast and from the point of view of design minimal vehicles attract more buyers than larger vehicles possessing several and more than adequate safety zones.
Increased demands for traffic safety have resulted in a modified basic construction of bumper bars. It is now common for the bar to have a closed cross-section. This shape of the bar results in the bumper bar absorbing collision forces and torsional loads and distributing strains in an optimal manner. The beam is primarily constructed for plastic deformation. The external dimensions of a bar with this construction become relatively large and the bar requires considerable space.
Previously known bumper bars are coated with at least one layer of material that makes the elastic deformation possible. The layer of material is soft and pliable such that collisions at low speed only result in an indentation. The layer of material where the indentation has occurred must subsequently spring back and return to its original shape. The layer of material often include plastics in the form of foamed polymers or similar. Other contributory materials and further layers are often used in addition to this in order to give stability, a protective surface, attractive appearance and other properties.
One problem with a bumper bar with such a layer of material is that the bar becomes voluminous. The layer of material must be relatively thick if it is to fulfill its function, and this involves a further increase in the size of the bumper bar.
Another problem with such a bumper bar is that it is expensive. The layer of material is expensive in itself, and the handling of the material and the bar during manufacture of the bar and the subsequent manufacture of the vehicle is expensive.
Further problems are that the layer of material normally exposed to the weather and the surroundings and tends to age before other parts of the vehicle. A layer of material that is damaged in a collision is difficult or impossible to repair which means that even if the bar is otherwise intact, the bar must be demounted and provided with a new layer of material. This involves further expense.
This invention solves these problems and offers a bumper bar with a basic construction that results in that the bar can be deformed elastically and/or plastically during a collision. According to the invention, a bumper bar is longitudinally extended and has an upper web, a lower web and a flange directed forwards in the normal direction of the vehicle. The flange is provided with grooves that are elastically deformable.